Some chars encoded during POST while others are not

Question

TL;DR

CodeIgniters' Security Class directly manipulates your Globals such as $_POST and it finds file() and file () to be a threat so it HTML encodes it.

// config.php from my apps folder is the culprit
$config['global_xss_filtering'] = TRUE;

Do-It-Yourself (the few, the brave)

In CodeIgniter 2.1.4 go to system/core/security.php and line #430-442:

/*
* Sanitize naughty scripting elements
*
* Similar to above, only instead of looking for
* tags it looks for PHP and JavaScript commands
* that are disallowed.  Rather than removing the
* code, it simply converts the parenthesis to entities
* rendering the code un-executable.
*
* For example:  eval('some code')
* Becomes:      eval('some code')
*/

$str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2(\\3)", $str);

Observation/question

Basically, it seems as though either PHP or Apache sees file () or file() as a threat.

Has anyone experienced this before or have documentation resources as to why this occurs?

Can anyone test this on their server to see if they experience the same behavior? I have tested this on both my Development and Testing machines. I have not had a chance to test on the Production machine because our clients connect to it.

Code

HTML

<input name="q1" type="text" value="Profile (61) (D)">
<input name="q2" type="text" value="(61) (D)">
<input name="q3" type="text" value="file (61)">
<input name="q4" type="text" value="fil (61)">
<input name="q5" type="text" value="file ()">
<input name="q6" type="text" value="file()">

JS - probably irrelevant

$.ajax({
    url: '/test_post'
    ,async: true
    ,cache: false
    ,type: 'POST'
    ,data: {
        q1: $('input[name="q1"]').val(),
        q2: $('input[name="q2"]').val(),
        q3: $('input[name="q3"]').val(),
        q4: $('input[name="q4"]').val(),
        q5: $('input[name="q5"]').val(),
        q6: $('input[name="q6"]').val()
    }
    ,dataType: 'json'
    ,success: function(data){
        console.log('irrelevant');
    }
});

Network - Headers tab in Chrome - Form Data section

q1: Profile (61) (D)
q2: (61) (D)
q3: file (61)
q4: fil (61)
q5: file ()
q6: file()

PHP - CodeIgniter 2.1.4 Framework

echo '<pre>'.$_POST['q1'].'</pre>'; // produces: Profile &#40;61&#41; (D)
echo '<pre>'.$_POST['q2'].'</pre>'; // produces: (61) (D)
echo '<pre>'.$_POST['q3'].'</pre>'; // produces: file &#40;61&#41;
echo '<pre>'.$_POST['q4'].'</pre>'; // produces: fil (61)
echo '<pre>'.$_POST['q5'].'</pre>'; // produces: file &#40;&#41;
echo '<pre>'.$_POST['q6'].'</pre>'; // produces: file&#40;&#41;

echo '<pre>'.html_entity_decode($_POST['q1']).'</pre>'; // produces: Profile (61) (D)
echo '<pre>'.html_entity_decode($_POST['q2']).'</pre>'; // produces: (61) (D)
echo '<pre>'.html_entity_decode($_POST['q3']).'</pre>'; // produces: file (61)
echo '<pre>'.html_entity_decode($_POST['q4']).'</pre>'; // produces: fil (61)
echo '<pre>'.html_entity_decode($_POST['q5']).'</pre>'; // produces: file ()
echo '<pre>'.html_entity_decode($_POST['q6']).'</pre>'; // produces: file()

// Both of these produce same exact result
echo '<pre>'.print_r($_POST, true).'</pre>';
echo '<pre>'.print_r($this->input->post(), true).'</pre>';

Browsers tested

• Chrome 31.0.1650.57 m
• IE 8
• FF 25.0

Server Information

Dev

• Widnows 7 x64
• Apache 2.2.17
• PHP 5.3.5

Testing

• Windows Server 2008 R2 x64
• Apache 2.2.21
• PHP 5.3.8

Answer 1

According to the user guide, you can get rid of this by setting

$config['global_xss_filtering'] = FALSE;

Or just remove this line.

IMHO, it's a design failure to modify the $_POST array, but there you go.